Brassinosteroids are plant hormones involved in multiple developmental processes. Brassinosteroids are involved in plant growth promotion, increase in the success of fertilization, shortening the period of vegetative growth, improvement of fruit quality, increase of stress resistance and improved crop yield.
Brassinosteroids are a group of naturally occurring polyhydroxy steroids. Natural brassinosteroids have a common 5-alpha cholestan skeleton and their structural variations come from the kind and orientation of functionalities on the skeleton, and from variations in the B ring. Brassinosteroids exert their activity by binding to the plasma membrane receptor kinase BRI1, resulting in the activation of a signaling pathway that involves a glycogen synthase kinase-3-like kinase (BIN2) and a serine/threonine phosphatase BSU1. BIN2 negatively regulates BR signaling by phosphorylation of the transcription factors BES1 (and probably the closely related BZR1), while dephosphorylation of BES1 by BSU1 activates the transcription of BR induced genes.
Due to their importance as plant growth promoting compounds, several companies developed production methods for brassinosteroids and analogues. Such methods have been disclosed, amongst others, in JP01075500, JP01175992 and U.S. Pat. No. 6,667,278.